Preheat the oven to 190C (375F). Spray a 24cm x 34cm sponge roll pan (or similar) lightly with oil. Line with baking paper and spray again. Lay a clearn tea towel on the bench and sprinkle generously with icing sugar.

Place the eggs and sugar in the bowl of an electric mixer. Using the whisk attachment, beat on high for 8-10 minutes until the mixture is very pale and thick (when you lift the beater a ribbon of mixture should fall onto the surface). Beat in the orange zest.

Sift over the flour and baking powder. Using a large metal or silicon spoon, gently fold in the dry ingredients (do not stir). Fold in the orange juice and melted butter. Pour the sponge mixture into the prepared pan and gently smooth the top.

Bake the sponge in the preheated oven for about 15 minutes until light golden and starting to shrink away from the sides of the pan (an inserted skewer should come out clean). While still hot, use a spatula to loosen the edges if necessary and turn the sponge out onto the prepared tea towel. While the sponge is still hot, peel off the baking paper and, using the tea towel to guide you, gently roll up the sponge lengthways. Lift the roll (along with the tea towel) onto a rack and leave to cool.

For the filling, beat all the ingredients until just combined – don’t overbeat.

When ready to serve, unroll the cooled sponge and spread with the mascarpone mixture. Roll up again, trim off the untidy ends and gently place onto a serving plate.

If making the icing, combine the icing sugar and orange juice until a thick, but pourable consistency is attained. Dip a fork into the icing and drizzle backwards and forwards over the sponge. Cut into slices to serve.